Without limiting the scope of the invention, its background is described in connection with creating thin film metal-oxide-semiconductor (MOS) field effect transistors, as an example.
Since the invention of the integrated circuit, work has been done to increase the number of components per unit of chip area, to improve device performance and to streamline the manufacturing process. The first integrated circuits were bipolar devices and used the junction isolation technique. However, as the demand for smaller and smaller devices increased, new technologies were developed which had higher packing density than bipolar devices. The metal-oxide-semiconductor devices have now substantially replaced bipolar devices where very high packing density is required, such as in memories and microprocessors. As the demand for faster, higher density metal-oxide-semiconductor devices continues, improvements in fabrication technology are necessary to keep pace with the demand.
Silicon-on-insulator (SOI) technology offers the highest performance for a given feature size due to the minimization of parasitic capacitance. Some of the SOI MOS field effect transistors have used a mesa configuration, others may use thick field oxide for isolation of the transistor. Various methods exist to create a mesa configuration. For further explanation on mesa configurations, see U.S. Pat. No. 5,087,580 issued to Robert Eklund on Feb. 11, 1992.
In addition, conventional SOI MOS field effect transistors use ion implanted source/drain regions. In order to ion implant the source/drain region, a photoresist layer is usually deposited and patterned over a silicon layer. Then the ions are implanted into the exposed silicon surface. The photoresist is then removed and the wafer is annealed. This results in comparable processing complexity to conventional bulk MOS field effect transistors just to make the source/drain regions.
Some of the problems faced have been related to the complexity of processing a conventional transistor. The complexity of the manufacturing process for a device, usually correlates to the price of manufacturing the device (disregarding the difference in cost of different materials).
Accordingly, improvements which overcome any or all of the problems are presently desirable.